Fused neutrals

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al hildenbrand said:
:blink:
Well, ya, that's what you are wondering about. You said that in the previous sentence,

And then you said that the eleven page PDF shed some light on it.

So, now that you are seeing light shed on what you are wondering about, in your own words, what are you understanding from the eleven page document?
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That people were receiving shocks from metal framed appliances, and thus, was a good idea to blow the supply fuse during such an event. The un-earthed (IT) system had a draw back, that when the first phase faulted, it became a TN system. So when the second fault occurred on a metal frame, dangerous potential to earth was inevitable. This necessitated that a conductor, preferably the neutral, be permanently connected to earth and the frame of appliances either connected to the neutral (TN-C) or a separate EGC (TN-C-S, TN-S, TT)
 
mbrooke said:
Do they make 660 watt incandescent lamps? As far as I'm concerned, its an arbitrary number- I mean imagine having to calculate a basement, laundry or closet pull chain as 660 watts.
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As far as I know, they don't make medium-base incandescent lamps any larger than 200 watts. The 660 watts apparently is a maximum rating for the power that can be drawn from a medium-base Edison socket, and would correspond to 6 amps at 110V.
Before they standardized plugs and receptacles, often appliances had an Edison type screw-in plug on the cord so that they could be powered off of a light socket like in the attached add for a waffle iron.
View attachment Waffle_iron_with_edison_screw-in_plug_2.pdf

Also attached are pages from a book on electrical wiring about the 660-watt Rule 35a in the 1915 NEC.
And for good measure, an add from 1922 that features an illuminated toggle switch which glows without consuming electrical power.

View attachment Rule35a_660watts_sockets_and_wiring_1917book.pdf

View attachment 660-watt_Rule_23d_1917book(2).pdf


View attachment Arrow_illuminated_switch(2).pdf
 
synchro said:
As far as I know, they don't make medium-base incandescent lamps any larger than 200 watts. The 660 watts apparently is a maximum rating for the power that can be drawn from a medium-base Edison socket, and would correspond to 6 amps at 110V.
Before they standardized plugs and receptacles, often appliances had an Edison type screw-in plug on the cord so that they could be powered off of a light socket like in the attached add for a waffle iron.


Also attached are pages from a book on electrical wiring about the 660-watt Rule 35a in the 1915 NEC.
And for good measure, an add from 1922 that features an illuminated toggle switch which glows without consuming electrical power.






Click to expand...

I've held these in my hand several times over the years as I use them in my garage:

https://www.acehardware.com/departme...E&gclsrc=aw.ds

https://www.amazon.com/GE-Lighting-7...s%2C143&sr=8-3

https://www.amazon.com/Sylvania-1574...gateway&sr=8-4


And while I've never held one in person, I did find this:

https://www.amazon.com/Halco-R40FL50...gateway&sr=8-8








https://www.amazon.com/SYLVANIA-1156...ateway&sr=8-13

https://www.amazon.com/EIKO-500W-PS...nt+light+bulb&qid=1569611624&s=gateway&sr=8-7

The photo flood bulbs last between 3-8 hours on the count the will put out tremendous lumen s and be switched on/off as pictures are taken.
 
mbrooke said:
I've held these in my hand several times over the years as I use them in my garage:

https://www.acehardware.com/departme...E&gclsrc=aw.ds
...........
...........

The photo flood bulbs last between 3-8 hours on the count the will put out tremendous lumen s and be switched on/off as pictures are taken.
Click to expand...


I was definitely mistaken about a 200 watt limit. And I forgot about the photo floods. They're a little bit more efficient with their higher temperature, but I remember the 500 watt ones putting out tremendous heat as well as light.
 
synchro said:
I was definitely mistaken about a 200 watt limit. And I forgot about the photo floods. They're a little bit more efficient with their higher temperature, but I remember the 500 watt ones putting out tremendous heat as well as light.
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Imagine what this would do to an enclosed fixture :eek::eek:

https://www.amazon.com/dp/B007ICMVPK/ref=nav_timeline_asin?_encoding=UTF8&psc=1

I thank you for posting those links. They to show fused neutrals as an option.

I sometimes wonder. If the US had chosen 220 volts early on, if for the first quarter of the 20th century homes would have been fed by two ungrounded conductors and businesses with 3 ungrounded conductors. Just seems like a brilliant idea for the time. I say that because 220 and 440 was so common in factories and some businesses.
 
synchro said:
I was definitely mistaken about a 200 watt limit. And I forgot about the photo floods. They're a little bit more efficient with their higher temperature, but I remember the 500 watt ones putting out tremendous heat as well as light.
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Its interesting, because before WWII, TONs of factories and small businesses were fed ungrounded delta. In fact the distribution system was 2.4kv or 4.8kv 3 wire ungrounded delta, feeding a delta-delta bank which then fed said place. This practice started falling out of favor, but as late as the 70s you could find the services new.
 

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synchro said:
I was definitely mistaken about a 200 watt limit. And I forgot about the photo floods. They're a little bit more efficient with their higher temperature, but I remember the 500 watt ones putting out tremendous heat as well as light.
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FWIW, the 4.8kv was ungrounded fed from local substations (6-12MVA) supplied by what I think was ungrounded 22kv prior to WWI, 23kv MGN Y today. Both the primary and secondary windings are delta.

http://www.ipernity.com/blog/connecticut_power_lines/4710756


In the late 1800s this utility used 11kv as subtransmission then going to 22kv:

http://www.ipernity.com/doc/connecticut_power_lines/20090161


Time and time again the pattern was to seal the system completely off from earth.
 
mbrooke said:
Its interesting, because before WWII, TONs of factories and small businesses were fed ungrounded delta. ...
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I've seen a few facilities with grounded delta circuits, and three-phase motors controlled with two-conductor contactors. The local oral history says that the practice was implemented during WWII to conserve scarce materials and produce more equipment faster.
 
drcampbell said:
I've seen a few facilities with grounded delta circuits, and three-phase motors controlled with two-conductor contactors. The local oral history says that the practice was implemented during WWII to conserve scarce materials and produce more equipment faster.
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They exist, but before and after ungrounded delta rained supreme, at least up north.
 
mbrooke said:
Maybe. But there was a time in history where fusing the neutral was the standard rather then the exception.

Somehow I doubt folks will believe me unless I post pics...
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In the District of Columbia I replaced several of these with modern panel boards. The asbestos lining scared me a lot more than the live front porcelain fuse holders and knife switches. I cannot vouch for this but I was told that these were originally supplied from Trolley power supply lines. Since that was three wire DC with rather high voltages I could understand their fusing the neutral conductor.

--
Tom Horne
 
GoldDigger said:
A delta system can have a grounded conductor, but cannot have a neutral. Would you call a wye-derived system with the neutral not brought to the service point a delta? I would not.
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I had a foreman on a small hotel project that pulled the feeder to the Fire Pump that way. When I tried to tell him that it had to have an undersized neutral conductor to serve as a fault clearing path he threatened to send me back to the hall to cool my heels until I learned some respect. I said Do It and began to pack up. He then said some other total BS and told me to get back to work. The Electrical Inspector on that job was as poorly trained as the foreman was. He had suggested that plastic boxes be used in the fire alarm conduit runs for their greater capacity and those being cheaper the foreman and the project manager were happy to accept his suggestion. I'm grateful that it was a limited energy fire alarm system because no provision was made for grounding continuity through those boxes. I lived in dread of the Inspector realizing his mistake and asking were the grounding bushings and jumpers were between the steel conduit entries into each plastic box. I was certain I was going to be assigned to install them while working through the finished single gang plaster rings. I'm pretty sure that I would have cut flat strap jumpers out of light weight steel sheets, slipped them in over each connector, then tighten the locknut back down over them.

The chief electrical inspector eventually came out on the job and then the real fun began. He required a witnessed re-pull of the conduit from the utility's pad mounted transformer to the Service Equipment listed Fire Pump Controller. The original field inspector tried to order a service equipment listed fused switch ahead of the fire pump controller because he didn't believe that any motor controller could also be the Service Disconnecting Means. I silently said Thank You Lord when the Chief inspector did not look behind any of the fire alarm devices and find those plastic boxes.

--
Tom Horne
 
hornetd said:
In the District of Columbia I replaced several of these with modern panel boards. The asbestos lining scared me a lot more than the live front porcelain fuse holders and knife switches. I cannot vouch for this but I was told that these were originally supplied from Trolley power supply lines. Since that was three wire DC with rather high voltages I could understand their fusing the neutral conductor.

--
Tom Horne
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Did they at least know what would happen if the neutral fuse blew before the live?
 
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